In internal combustion engines with externally supplied combustion ignition, usually spark plugs are installed in the combustion chamber of the internal combustion engine, the spark plugs essentially being composed of terminal stud, insulator, shell, and electrodes. The insulator is inserted in the tubular metallic shell, in the central bore of the insulator, in turn, an inner conductor arrangement being inserted which is composed of a central electrode on the combustion chamber side and of the terminal stud, which is distant from the combustion chamber. In this context, the rotationally symmetric axes of the shell, of the insulator, and of the inner conductor arrangement coincide. Mounted to the shell are the at least one ground electrode on the combustion chamber side so that an ignition spark forms between the central electrode and the ground electrode in response to the application of a high voltage, the spark assuring the ignition of the combustible mixture in the combustion chamber of an internal combustion engine. Usually, the ignition voltage is made available inductively by an ignition coil which assures that the voltage at the electrodes of the spark plug increases very heavily in response to disconnecting the ignition coil charging space. The function of the spark plug is to introduce the ignition energy into the combustion chamber, and to initiate the combustion of the air/fuel mixture by the electric spark between the electrodes. During the operation of the spark plug, voltages of up to over thirty Kilovolts can occur. The residues separating from the combustion process such as soot, oil, carbon, and ash from fuel and oil, are electrically conductive given certain thermal conditions. Nevertheless, no sparkovers or breakdowns may occur across the insulator in these conditions. For this reason, the electrical resistance of the insulator must be sufficiently high up to 1000xc2x0 C. and may not change during the service life of the spark plugs.
Besides providing the ignition voltage inductively, it is known to generate an ignition spark by radio frequency ignition as described in SAE paper 970071 xe2x80x9cInvestigation of a Radio Frequency Plasma Ignitor for Possible Internal Combustion Engine Usexe2x80x9d. Here, the possibility of generating ignition sparks using radio frequency ignition is described. In such a radio frequency ignition, which is also called microwave ignition, a high voltage is generated by low-resistance infeed at the hot end of a quarter-wave line of an RF resonator.
In contrast, the igniting device according to the present invention has the advantage of a simple coupling out for an ion current and of a particularly simple design, respectively. Both the oscillator and the high-voltage section are advantageously seated on a shared substrate. The capacitor can likewise be arranged between the waveguide patterns on the substrate. Thus, a simple manufacture is possible, and the requirements for high-voltage strength can be taken into consideration by a corresponding form design and/or insulation level.
It is particularly advantageous to use a flexfilm as the substrate for jointly mounting the high-voltage section and the oscillator portion. Such a flexfilm offers the possibility of very simple and cost-effective manufacture.
FIG. 1 shows the principle of the radio frequency ignition.
FIG. 2 illustrates one embodiment of the present invention.
FIG. 3 illustrates another embodiment of the present invention.
FIG. 4 illustrates another embodiment of the present invention.
FIG. 5 illustrates another embodiment of the present invention.
FIG. 6 illustrates another embodiment of the present invention.
FIG. 7 illustrates another embodiment of the present invention.
FIG. 8 illustrates another embodiment of the present invention.